Mr Houghton said the Mustang had not been flying too close to the ground prior to the crash.

He said that there appeared to be a "problem with the aircraft that caused it to go out of control".

"This is a very large incident, probably one of the largest this community has seen in decades," Stephanie Kruse, a spokeswoman for the Regional Emergency Medical Service Authority, told the Associated Press.

"The community is pulling together to try to deal with the scope of it. The hospitals have certainly geared up and staffed up to deal with it."

She said 15 of the injured were in a critical condition.

Kathy Carter, a spokeswoman for Renown Medical Center in Reno, said that two people had died, not including the pilot.

Earlier unconfirmed reports said up to 12 people might have been killed.

The Mustang, named The Galloping Ghost, was flown by well-known racing pilot Jimmy Leeward, 74.

Image caption
Jimmy Leeward started racing planes in the 1970s

Mr Houghton said that Mr Leeward, from Ocala, Florida, was a property developer who had been racing planes since the mid-1970s.

He said that Mr Leeward's medical records had been "in tip-top condition".

He added that most of Mr Leeward's family had been at Friday's event.

Nevada Governor Brian Sandoval arrived at the scene and praised the emergency services for their "flawless reaction to what happened".

Mr Leeward's website says he had flown in more than 120 races and had been a movie stunt pilot.

Ronald Sargis, who was sitting in the box-seat area, said spectators could tell the plane was in trouble before it crashed.

"About six or seven boxes down from us, it impacted into the front row," Mr Sargis told KCRA-TV in Sacramento. He added: "It appeared to be just pulverized."

Jeff Martinez, a local weatherman who was just outside the air race grounds, said he saw the plane veer to the right and then crash into the ground.

'Unbelievable gore'

The Reno Gazette-Journal website had posted a witness video of the crash from YouTube, but YouTube has now withdrawn it, saying it breached its terms.

Eyewitness Dr Gerald Lent, of Reno, told the newspaper: "It's just like a massacre. It's like a bomb went off. There are people lying all over the runway."

Maureen Higgins of Alabama, who has been coming to the show for 16 years, told the Associated Press that the pilot was on his third lap when he lost control.

National Guard members who were already on site helped with the response, air show spokesman Mike Draper told CNN.

Democratic Nevada Senator Harry Reid issued a statement saying he was "deeply saddened" about the tragedy.

"My thoughts are with the families of those who have lost their lives and with those who were wounded in this horrific tragedy," he said.

The National Championship Air Races are held every year in September in Reno.

There have been safety concerns in the past, with four pilots killed in 2007 and 2008.

However, organisers and aviation authorities say they spend months in preparation for the event.